I. Field of the Invention
The present invention relates to compositions and systems comprising quaternary organopolysiloxanes that can be useful for demulsifying and separating aqueous emulsions and water-in-oil emulsions formed during processing of organic materials such as bioproducts.
II. Technical Considerations
Bioprocesses can be used to produce a wide variety of bioproducts, such as pharmaceuticals, insecticides, food additives, solvents, fuels, etc. Bioprocesses can utilize renewable feedstock sources such as corn, grain, algae, and other naturally occurring organic sources, and offer the potential for an environmentally friendly and less costly alternative to conventional synthesis routes that rely on petroleum-based feedstocks. The ability to produce a valuable end product via a biological process, using microorganisms such as bacteria, fungi, mold, etc., is proving to be a promising approach for a growing number of derived products.
Bioproducts such as antibiotic pharmaceuticals (for example penicillin) or substances obtained from microorganisms such as bacteria, algae or fungi (for example spinosyns, streptomycin, erythromycin, efrotomycin, etc.), can be produced by fermentation of a culture of microorganisms and/or enzymes in a nutrient-rich media. The bioprocess produces a bio-broth comprising a complex mixture of organic and inorganic compounds such as the valuable bioproduct, the biomass of microorganisms or enzymes, unconverted nutrient medium, fats, proteins, carbohydrates, amino acids, water and surfactant. Thus, the desired bioproduct must be extracted from the undesirable components of the bio-broth.
The separation of the selective components from bio-broths is often performed using liquid-liquid extractions. An extracting solvent, typically a water immiscible organic solvent such as amyl acetate, methyl ethyl ketone, methyl isobutyl ketone, amyl alcohol, butyl alcohol, toluene, heptane or benzyl alcohol, is added to extract the desired bioproduct from the aqueous phase to the organic phase, and the phases are separated. The broth components can form a stable emulsion as the broth and solvent are mixed which is difficult to separate by physical means, for example mechanical separation devices such as settlers, decanters and centrifuges. The resulting emulsion can occur as a dispersion of an organic phase within the aqueous phase, a dispersion of the aqueous phase within the organic phase, or both types of dispersions can be present. The dispersed material, including organics such as microorganisms, enzymes, proteins, lipids and carbohydrates, can possess a net negative charge or exhibit both polar and non-polar characteristics and be difficult to separate. These types of molecules can form hydrogen bonds with polar solvents, such as the polar aqueous phase, while having non-polar regions which can be soluble in organic solvent present in the less polar or non-polar organic phase. This results in an emulsion which is relatively stable and difficult to separate.
Nevertheless, depending on the components, some emulsions eventually break by themselves, that is, such emulsions have only “temporary stability” and over time and with the aid of gravity or centrifugation, the emulsion separates into distinct layers. More commonly, a demulsifier is added to encourage or initiate separation by gravity or centrifugation. Sodium chloride or another inorganic salt or an organic demulsifier such as AKZO D5430 quaternary fatty acid amine (commercially available from Akzo Nobel Chemical, Inc.), or KR-L255 alkylphenol-formaldehyde resin (commercially available from Kroff Chemical Co.) can be employed as a demulsifier.
Whether treated mechanically or chemically, upon separation, a solvent phase and an aqueous phase are formed. Optionally, a solid phase can be present. The solvent phase can comprise the desired bioproduct, solvent and small amounts of water and other impurities, such as organic material, the structure of which may be similar to that of the desired bioproduct and other undesirable components dissolved in the solvent. The aqueous phase can comprise the remaining components, including the biomass of the microorganisms or enzymes, and there may be a small amount of the desired bioproduct dissolved in the water and contained in the biomass. Alternatively, the desired bioproduct can be present in the aqueous phase rather than in the solvent phase.
The solvent phase may be cleaned further after separation from the aqueous phase by performing additional extractions that can include adjusting the process conditions, for example pH, temperature, or the addition of other solvents to drive the equilibrium in the desired direction to enhance the isolation of the desired bioproduct. If the addition of water forms a secondary emulsion, separation may be accomplished as described for the first emulsion. When the phase containing the desired bioproduct has been cleaned to the desired level, excess solvent or water, depending on the phase in which the bioproduct is present, can be removed by evaporation.
Conventional methods for demulsification and separation of phases have several drawbacks. For example, although inorganic salts such as sodium chloride are routinely used as demulsifiers, the phase separation can take place more slowly than desired, and the separation tends to involve a relatively large, indistinct interface, with poor segregation of components into the separate phases. For example, a significant portion of the desired bioproduct is often entrapped within cells of the biomass. As a result, recovery of the bioproduct typically has been found to be as low as 80%.
Similar emulsions also may be encountered in other bioprocessing applications, wastewater treatment or oil recovery. For example, emulsions can form during liquid extraction of plant materials (such as plant oils) from plant tissues. In crude oil production processes, water-in-oil emulsions can form in the presence of naturally occurring polar surface-active molecules such as asphaltenes and resins; fine solids such as crystallized waxes, clays and scales; steam injection; and/or high shear conditions, for example at the wellhead in the choke valve.
Use of conventional demulsifiers, such as alkylphenol-formaldehyde resins which contain phenol groups, can pose environmental concerns. Such systems are often formulated with aromatic solvents to improve the flow properties of the demulsifier, however, aromatic solvents such as benzenes, xylenes, naphtha or napthalenes also can present environmental concerns. As environmental regulations become more stringent, there is a need for more environmentally friendly or “green” demulsifiers which quickly separate phases in emulsions, provide a well-defined interface to facilitate separation and that do not require centrifugation to separate the phases of the emulsion.